The present invention pertains to sealing devices or systems wherein the seal per se is relatively soft, flexible or deformable. In particular, the invention deals with an improved means for presenting undesired extrusion of such seals. When such a sealing device is in place between the two rigid surfaces against which it is intended to seal, the pressure being sealed against may tend to extrude the seal material out of its intended position, e.g. in a groove or the like in one of the two surfaces, and into a smaller adjacent clearance between the two surfaces. This can lead to deformation of the seal, damage to the seal, and/or loss of sealing effectiveness.
In the past, one technique for dealing with such undesirable extrusion has been to place a rigid retainer member adjacent the relatively soft seal device. For example, if the seal device is an annular member, the retainer might be a rigid washer or the like. However, it is generally preferable to utilize a one-piece seal, e.g. for ease in handling, installation, and servicing. Accordingly, there have been various prior attempts to devise one-piece seals including relatively soft sealing sections and harder anti-extrusion sections. In some cases, the two sections have been bonded together, while in others, they have been separately formed so that they can be snapped together by means of undercut grooves or the like. However, these designs can present additional problems, particularly as the two sections can fairly easily become separated and/or misaligned in use. Additionally, these prior art seals are expensive inasmuch as the adhesives used for bonding are costly and tooling to make the seals employing indirect grooves can present design problems.